In North America, consensus regarding the association between workplace exposures in aluminum smelters and the diagnosis of obstructive lung disease has not been reached. Previous studies have been limited by a lack of preexisting health information, reliance on variable diagnostic methods and the unclear impact of the healthy worker effect. This historic/prospective longitudinal cohort study of workers from Alcoa, the world's largest aluminum producer, integrates multiple datasets-including a human resources database, an onsite clinic database, an industrial hygiene database, medical records and spirometry records- and explores the relationship between the diagnosis of obstructive lung disease, longitudinal changes in spirometry and the multiple exposures present in aluminum smelters, particularly total and respirable particulate matter. Specific Aim 1. Delineate an overall and inception cohort of exposed smelter workers. Specific Aim 2. Determine change over time in spirometric function in both cohorts. Specific Aim 3. Measure incidence and prevalence rates of obstructive lung disease in both cohorts using insurance claims data. Specific Aim 4. Determine concordance between change over time in spirometric function and diagnosis of obstructive lung disease in both cohorts. Specific Aim 5. Measure the association between exposure to total and respirable particulate matter and both the diagnosis of obstructive lung disease and change over time in spirometric function in both cohorts. Specific Aim 6. Measure the association between other exposures-including fluoride, sulfur dioxide, oil mist and coal tar pitch volatiles-and both the diagnosis of obstructive lung disease and change over time in spirometric function in both cohorts.Specific Aim 7. Explore the role of smoking as an effect modifier of change over time in spirometric function and the diagnosis of obstructive lung disease. Specific Aim 8. Develop multivariate models that include demographic data, smoking status and the exposures to predict decline in spirometric function and the incidence of obstructive lung disease. [unreadable] [unreadable] [unreadable]